Shareholders' Equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Summary of Changes in Shareholders' Equity
Balance, value			$ 372,169
Net earnings	3,626	15,202	10,111	26,588
Dividends			(4,202)
Stock-based employee compensation expense, value			372	311
Balance, value	378,450		378,450
COMMON STOCK [Member]
Summary of Changes in Shareholders' Equity
Balance, value			334
Balance, shares			33,394,395
Stock-based employee compensation expense, shares			440
Balance, value	334		334
Balance, shares	33,394,835		33,394,835
PAID-IN CAPITAL [Member]
Summary of Changes in Shareholders' Equity
Balance, value			460,687
Stock-based employee compensation expense, value			372
Balance, value	461,059		461,059
DIVIDENDS PAID IN EXCESS OF EARNINGS [Member]
Summary of Changes in Shareholders' Equity
Balance, value			(88,852)
Net earnings			10,111
Dividends			(4,202)
Balance, value	$ (82,943)		$ (82,943)